1. Field
Embodiments of the present invention relate to a non-linear gamma compensation current mode digital-analog converter and a display device including the same.
2. Description of the Related Art
The organic light emitting diode (OLED) display device uses OLEDs in which a luminance is controlled by a current or a voltage. Each of the OLEDs includes an anode layer and a cathode layer, which form an electric field, and an organic light emitting material, which emits light because of the electric field.
In general, OLED display devices are classified into a passive matrix OLED (PMOLED) and an active matrix OLED (AMOLED) in accordance with a method of driving OLEDs. The PMOLED display is driven by forming positive electrodes and negative electrodes that cross in a matrix and selecting a line. The AMOLED display is driven by coupling a thin film transistor and a capacitor to the organic light emitting diode and maintaining the voltage by the capacitor. Depending on the type of signal applied to the capacitor to maintain the voltage, the AMOLED method may be classified into a voltage programming method or a current programming method.
However, a pixel circuit according to a conventional voltage programming method has the disadvantage of expressing high-level gray levels due to variations of a threshold voltage of the thin film transistor and mobility of a carrier, the deviation being generated as a result of a non-uniform manufacturing process of the thin film transistor. On the other hand, although the amount of current and voltage supplied from a driving transistor in each of the pixels is not uniform, the pixel circuit employing the current programming method can provide panel uniformity as long as current supplied from a current source to the pixel circuits is uniform.
When utilizing a display device by using the pixel circuit that employs the current programming method, a digital-analog converter is required to convert gray level data into gray level current to apply the gray level current to the pixel circuit. When converting the gray level data into the gray level current, the digital-analog converter must perform a gamma correction for the gray level data by considering the gamma characteristic of the display panel.
The gamma characteristic of the display panel is non-linear for the gray level data, and in contrast, the conventional digital-analog converter outputs a linear gray level current for the gray level data. In this case, the display panel may not display the image of the desired gray level and display quality may be deteriorated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.